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TPS2378: some questions about the specification

Part Number: TPS2378

Hello,

Our customer has 4 questions about TPS2378.

1.What is the maximum power consumption after PD detection after detection and classification?

2.Is T2P pin open for class 2 case?

3.Regarding the selection of RAPD 1 and RAPD 2, our AC adapter is 27 V.

  In this case, how can they choose the resistance value?

4.Is the diode DA mounted on the AC Adapter side of the circuit diagram in the data sheet for backflow prevention?

  Is it a mandatory item?

Please teach if you know.

Thank you.

  • Hi Mayumi,

    1. Are you asking for for the power consumption of the IC while power is being delivered? In that case, that answer will depend on the current input voltage (42V-57V). Multiple the bias current (285-500uA) (pg. 6 of www.ti.com/.../tps2378.pdf ) by the current input voltage to get your expected power consumption of the device, only.

    2. T2P is just an indicator. You may leave it open if you would like, but would stay high since class 2 is type 1, not type 2. Type 2 would be the class 4 only (25W at PD).

    3. See section 8.2.2.6 for resistor selection. Your goal is to maintain the voltage division ratio to get 27V to 1.5V at APD while using larger resistors to reduce power consumption.

    4. Yes, it is an ORing diode. For more info on Oring in PoE, see this app note: www.ti.com/.../slva306a.pdf

    Hope this helps!
    Thomas A.
  • Dear Thomas,

    Thank you very much .
    Your kind response is very helpful. I will tell customers.

    Thank you.
    Mayumi